[Make-wifi-fast] Wiring up a wireless testbed

Bob McMahon bob.mcmahon at broadcom.com
Sat Nov 4 22:04:56 EDT 2017

Also, the final piece of the puzzle is chip power consumption.    Monsoon
makes a current meter for a reasonable price.

I realize the focus here is on low latency.   The market is also driving
power consumption, i.e. "energy consumed for useful information energy
successfully delivered with the lowest latency possible."  The chips
themselves can give the RF energies (as well as dump h matrices) so having
an expensive network analyzer for that isn't required beyond chip design.


On Sat, Nov 4, 2017 at 6:56 PM, Bob McMahon <bob.mcmahon at broadcom.com>

> Also, Ixia is selling a controllable RF system and it's in early stages.
> Maybe contact them to see what the market is driving them to build?   My
> guess is their asking price will exceed $100K and has huge margins relative
> to bill of materials.
> One could probably work with telemakus and build a few using their parts
> and sell it for cheaper than the IXIA chassis and still make a nice profit.
> Bob
> On Sat, Nov 4, 2017 at 6:50 PM, Bob McMahon <bob.mcmahon at broadcom.com>
> wrote:
>> Try telemakus <http://www.telemakus.com/> for variable attenuators and
>> variable phase shifters.    Aeroflex works well to though are a bit more
>> expensive, e.g. the 8331
>> <http://weinschel.apitech.com/weinschel/pdfiles/wmod8331.pdf> is an
>> example
>> Power dividers, splitter/combiners and butler matrix devices are sold by
>> multiple vendors.  Prices will vary. Unfortunately, prices aren't super
>> low.  But usually it's worth the extra money to get a reliable and
>> controllable test bed, particularly when one values their time into the
>> equation.
>> Bob
>> On Sat, Nov 4, 2017 at 2:48 PM, Toke Høiland-Jørgensen <toke at toke.dk>
>> wrote:
>>> Bob McMahon <bob.mcmahon at broadcom.com> writes:
>>> > A way I think about is to emulate the "system" in both range/power
>>> > (attenuation) and in mixing (phase shifts)   It's a diagonal matrix for
>>> > range feeding into an h-matrix for the mixing.  A butler matrix can be
>>> used
>>> > for the latter if variable phase control isn't required, e.g. you don't
>>> > care about spatial stream relative powers.
>>> >
>>> > On adding energy for "random" noise, some knobs of concern are the
>>> energy
>>> > detect on the tx and signal floor for the rx.   These sources can be
>>> fed
>>> > into the same h-matrix through their own d-matrices.  This won't
>>> replace
>>> > field tests but helps get closer towards that while providing for
>>> repeat
>>> > ability.
>>> What equipment would it take to do something like that?
>>> > Also, equally important by my judgment, though not related to
>>> wireless, is
>>> > to synchronize the clocks on the PCs.  An oven controlled oscillator
>>> and
>>> > PTP works well towards that goal.
>>> Yeah, already using PTP in my testbed; quite essential for measuring
>>> one-way delay.
>>> -Toke
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